Evidence of microplastics in the Chi River Basin, Thailand: Anthropogenic influence and potential threats to edible arthropods

Microplastics (MPs) are an emerging pollutant in freshwater that have become a cause for concern among researchers around the world. In this study, MPs contamination in water, sediment and edible arthropods of the upper Chi River and Pong River was studied to analyze the influence of anthropogenic activities on contamination in the river environments and arthropods. Five species of arthropods were observed to assess the impact of MPs contamination: Caridina sp, Macrobrachium sp., Aethriamanta sp., Aciagrion sp. and Sphaerodema molestum. MPs were found in water and sediment samples with an average of 141 items/m³ and 9.5 items/kg, respectively. Fibers were major MPs shape in water (63%) and sediment (81.9%). MPs with dark blue color were numerically dominant in water (28%) and sediment (39.6%). MPs in edible arthropods were in the range of 0.25 – 8.0 items/individual. A wider variety of polymer types was found in the rivers than in the edible arthropods. Overall, dark blue colored PP fibers were found to be the most abundant in water, sediment and edible arthropods with MPs mostly ranging 1000–2000 µm in size. MPs concentration in water correlated with community size (p-value <0.05), and the abundance in sediment correlated with the number of roofs (p-value <0.05) and the distance of the rivers from communities (p-value <0.05). Anthropogenic activities significantly contributed to abundance of MP in water and sediment. Industrial, community and fish farming contributed to MP in water and agriculture and community directly correlated with MP in sediment with p-value <0.05 at 95% confidence. The results indicate the significant influence of anthropogenic activities on the amount of MPs in water and sediment, directly relating to contamination in edible arthropods. Domestic wastewater and plastic waste are likely to be the leading causes of existing MPs in the rivers and arthropods.